The present invention relates to a proportional electromagnetic valve for controlling flow rate, direction, shut-out, pressure, and the like of a fluid by driving solenoids in accordance with an external command signal and, more particularly, to a structure of a proportional electromagnetic valve having therein an amplifier to selectively drive solenoids.
FIG. 1 shows an example of a conventional proportional electromagnetic valve having therein an amplifier with a part cut away. FIG. 2 shows a plane view wherein the lid of an amplifier unit is removed.
In FIG. 1, reference numeral 10 denotes a valve main body; 12-1 and 12-2 indicate solenoids; 14 is an amplifier unit having therein an electric circuit to selectively drive the solenoids 12-1 and 12-2; 16 a casing; 18 a lid of the casing 16; 20-1 and 20-2 are printed circuit boards on which a drive amplifier is attached; 22 a display plate on which volume adjusters and display lamps are arranged; and 24-1 and 24-2 cable lead-in ports.
As shown in FIG. 2, which illustrates the amplifier unit with the lid 18 removed, concave portions 26 are formed at four positions on the side surfaces of the casing 16 of the amplifier unit 14. The concave portions 26 are provided so as to insert bolts from the upper portion of the casing 16 when the valve main body 10 of FIG. 1 is attached to an apparatus to be controlled.
In the conventional proportional electromagnetic valve having therein an amplifier, the solenoids 12-1 and 12-2, which drive valve members provided in the valve main body 10, are attached to both sides of the valve main body 10. The amplifier unit 14 is mounted on the valve main body 10. The valve main body 10 is fixed by bolts to an arbitrary apparatus to be controlled. The bolts extend along the four concave portions 26 formed on the side surfaces of the casing 16 into the valve main body 10.
The electric circuit provided in the amplifier unit 14 selects either one of the solenoids 12-1 and 12-2 in accordance with the controlling direction based on an external DC electric signal. The electric circuit then corrects an activation response characteristic by a ramp circuit or the like and, thereafter, it adjusts a drive current which is sent to the solenoid 12-1 or 12-2. Thus, the opening/closing speeds and opening degrees of the valve members in the valve main body 10 are controlled.
The drive amplifier of the amplifier unit 14 is attached to the printed circuit board and provided in the casing 16.
As shown in FIG. 2, the concave portions 26 are formed at four positions on the side surfaces of the casing 16. The enclosing space in the casing 16 is narrow and the size of the printed circuit board which is assembled in the casing 16 is also small.
Therefore, the printed circuit board is divided into a plurality of printed circuit boards 20-1 and 20-2 (in this example, two boards). These printed circuit boards are assembled as a solid configuration or a multi-stage structure as shown in the diagram and are mutually connected by wires.
Consequently, there are problems in that the wiring connection among the plurality of divided printed circuit boards and the assembly thereof become complicated and, further, since the printed circuit boards are closely arranged, mutual interferences are caused among the circuits.
On the other hand, since the size of the printed circuit board is small, a drive amplifier which can be attached thereon is limited. For example, the drive amplifier is limited to a circuit which operates only by a DC input signal and a drive amplifier which can operate by contact signal inputs cannot be attached. Accordingly, sufficient circuit function cannot be provided and, moreover, another circuit cannot be extended.
Therefore, a type of input signal cannot be selected in accordance with an apparatus to be controlled and the control characteristic cannot be changed in accordance with the controlling direction. As such, there is a problem such that the foregoing conventional system can only be used for a special application.